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SPECIATION
The 5th Idea of Natural Selection
SPECIATION
Formation of a new species
Most new species are formed through a three-stage
process called ALLOPATRIC SPECIATION
Allop. Spec. – STEP #1
A genetic or physical barrier separates a population
into two groups that are isolated from each other.
Isolated groups do not mate with each other, ensuring
that mutations within one group are not passed to the
other.
Physical barriers between groups could be natural
(mountain ranges, ocean, canyons, rivers) or manmade (dams, canal, cities)
Allop. Spec. – STEP #1
Another barrier that can occur is DNA mutation
changing the number of chromosomes an organism
has.
Allop. Spec. – STEP #2
Natural selection works on both groups independently
resulting in differences in two groups.
The larger the differences in their environments, the
more differences will be visible between the two
species.
Allop. Spec. – STEP #3
The two species are formed due to an increase in the
physical and behavioral differences accumulated by
each species.
Both groups will no longer be sexually compatible an
unable to produce fertile offspring…
TWO NEW SPECIES HAVE BEEN FORMED
Example! Darwin’s Finches
Darwin discovered 13 different finch species when
travelling in the Galapagos Islands.
All species were approximately the same size (15-20
cm) and are brownish/black in color.
BUT EACH SPECIES HAS….
beaks of different size and shape.
different mating behaviors.
different song melodies.
Wood Bison & Plains Bison
Originally shared one common ancestor before
population was split into two groups.
Wood bison live in woods of Northern Canada
(population focused around Wood Buffalo National
Park).
Plains Bison are found in Southern Prairie provinces
and majority of the US.